A couple of weeks ago, before a service, I had been (very quietly) practicing a particular hymn that had been giving me trouble.
The service started. I started with said hymn. Dead silence from the congregation ... "weird" I thought - it's a well known hymn ... why aren't they singing? ... I carried on regardless.
When done, completely mystified ... I moved the sheet music of said hymn to the back of my little 'arrangement' and brought the next hymn music to the front. In doing so, I realised with utter horror, that said hymn was supposed to have been played at the recession!!! I had gotten my sheet music muddled and had not checked that I had put the order right before the service! One mistake never to be repeated!